This is a randomized two-group repeated measures controlled clinical trial to evaluate the effects of a nurse-run home-based exercise intervention for HIV seropositive men and women 18 years of age and older with CD-4 cell counts between 200 - 500/mm3 on: (1) physical endurance (oxygen consumption, (2) subjects perceptions of both their functional status and well-being using validated scales (Sickness Impact Profile; Medical Outcomes Study-HIV Health Survey) and daily dairy reports, and (3) immune status (CD-4 cell count and CD-4 percent). Both the treatment group and the control group will be tested at baseline (week 0) and at 8, 15 and 19 weeks after study group assignment for the purposes of data collection. Both groups will receive usual medical and nursing care from their regular providers. Both groups will also keep daily diaries of selected symptoms, mood, and exercise routines from baseline through study exit with weekly pick-ups of the diaries. In addition, the treatment group will receive an exercise regimen which will include warm- up movements; either a 20 minute work-out on the Fit-One exercise tract or a walking program (if unable to use the exercise track); and cool-down movements, all done under nursing supervision three times a week for fifteen weeks. Several levels of analyses will be conducted. First, bivariate analysis will examine relationships between the covariates and the dependent variable, peak oxygen uptake, by Student's t-test. Second, change in peak oxygen uptake will be examined by a two-sample t-test. Third, t- test statistics will be used to assess the association between measures of functional status and well-being and intervention group status. Fourth, the means of numbers of symptom-days from the diary will be compared between groups by t-test statistics. Fifth, variables hypothesized to predict enhanced immune function will be examined in a multivariate regression model to examine interaction effects. This study is important for several reasons: 1) it proposes to prospectively study the effects of exercise on physical endurance, quality of life, and immune status for the first time in an HIV seropositive diverse sample os subjects including a substantial number of African-Americans, women, and intravenous drug users, 2) it is a nurse-run home-based intervention that can be readily completed by individuals in a variety of living situations and with limited resources, and 3) analysis of daily measures of physiologic and psychologic status from diary recordings will result in an examination of patterns of "minor" symptoms for their association with the effects of the intervention.